The present invention provides a method for non-invasively determining dimensions of a lesion within soft tissue. Specifically, the present invention provides a transmissive ultrasound system having a holographic imaging detector.
Breast cancer screening techniques have been limited to mammography because screening techniques need to be economical in order to achieve widespread use. However, mammography often has a high incidence of false positive readings that often prove to be benign or fluid-filled cysts that do not require surgical intervention or other highly invasive therapeutic procedures. It is widely-accepted that late-stage breast cancer detection is associated with significantly increased morbidity and mortality. Despite extensive research, new diagnostic classification systems and improved detection methodologies, there is still a great need to detect small neoplasms (typically 5 mm or smaller) accurately, quickly, non-invasively and inexpensively and with a good idea of size during the early detection process. Failure to detect such early breast cancers is associated with more invasive therapeutic interventions at higher risk and higher expense.
X-Ray mammography is the accepted standard screening tool for diagnosis of breast cancer. It has good resolution and clarity, is capable of detecting microcalcifications and sometimes delineates the borders of some masses. However, 60-80% of subsequent biopsies recommended from mammography result in benign diagnoses. Thus, there is a need in the art to improve the positive predictive value of conventional breast imaging.
Mammography is also less sensitive for detecting cancers in women with mammographically dense breast tissue. Since the more dense, fibrous tissue can obscure neoplasms, mammograms are often inconclusive or inaccurate in these women. Thus, there is a need in the art to more accurately detect neoplasms in women with dense breasts.
In addition, mammography is an invasive procedure that should not be done too frequently in view of a cumulative effect of radiation doses. Many women are hesitant to be imaged because of a risk or even a perceived risk associated with exposures to radiation. Moreover, there is significant discomfort associated with a mammography procedure because the breasts have to under go significant compression that can also distort lesions, if present and flexible. Therefore, there are some significant shortcomings to mammography as a standard means for breast cancer screening.
One alternative to X-Ray mammography is conventional, reflective ultrasound using a pulse-echo technique. Generally, breast sonograms using reflective ultrasound are used to characterize masses (such as whether they are cystic or solid) detected by physical exam or by mammography. There is still debate within this field whether reflective ultrasound is able to predict benign from malignant solid masses. Moreover, reflective ultrasound is operator-dependent, time-consuming, and a full image of the breast cannot be obtained or even stored for later reference. Further, sonography is not useful for the assessment or detection of microcalcifications, often the only sign of early in situ ductal carcinomas.
Therefore, there is a need in the art to overcome these problems associated with early screening of breast cancers and obtain more information and more reliable information, such as lesion size if one is found, from the early screening procedure to better guide follow up and to relieve the extreme anxiety of patients who have something found but have a greater than 50% chance that it is benign or nothing, but is learned days or weeks later. Thus there is a need for more statistically reliable information, such as lesion dimensions, to be obtained during the early and non-invasive screening process and not be determined during follow up procedures which are usually invasive. During initial comparative procedures with mammography and reflective ultrasound, the present procedure of transmissive ultrasound was surprisingly found to not only identify lesions with better accuracy and visualization than either of the other two imaging modalities but also more accurately determine lesion dimensions, a surprising result.
The present invention provides a method for non-invasively determining dimensions of a lesion within a soft tissue object, comprising:
(a) ultrasonically imaging the object in an apparatus having an acoustic transducer, an acoustic focussing system, a holographic imaging detector, and a means for visualizing the holographic image;
(b) obtaining a holographic planar image of a lesion in a first plane having a thickness z and having a dimension across a wide area of the lesion of x and a length across the lesion of y wherein y is at an approximately 90 degree angle to x;
(c) determining if the image of the lesion within the object is contained in different planar images;
(d) measuring the x and y dimensions of the lesion in the plane having the largest sum of x plus y dimensions; and
(e) determining the 3-dimensional size with a means for z-axis measurement.
Preferably, the object is breast tissue. Preferably, the holographic planar image of a lesion in the first plane in step (b) uses all three axes to be orthogonal. Preferably, the apparatus contains a holographic detector element for imaging in an optical mode the distortions cause by transmissive acoustic through the soft tissue. Preferably, the means for z-axis measurement is to either determine numbers of planes traversed of a known thickness, or rotating the object (patient or body segment) such that the z-axis becomes a third dimension with an additional x-y axis measurement at about 90 degrees rotation, or both.
The present invention further provides a method for guiding a biopsy device in soft tissue to a lesion, comprising ultrasonically imaging the soft tissue in an apparatus having an acoustic transducer, an acoustic focussing system, a holographic imaging detector, and a means for visualizing the holographic image to simultaneously visualize both the biopsy device and the lesion site. Preferably, the apparatus contains a holographic detector element for imaging in an optical mode the distortions cause by transmissive acoustic through the soft tissue.